#quasiparticle

Unusual ‘Quasiparticle’ Uncovered in Common 2D Material

The discovery of a new quasiparticle is analogous to the discovery of a new molecule, except molecules contain different elements, while quasiparticles are made from fundamental particles and interactions. As each molecule has its own unique properties, so do quasiparticles, and the discovery of a new one brings a range of possible technological applications. 

A new quasiparticle named…

Scientists discover new quasiparticle called a “quantum droplet” or “dropleton”

Photograph by Tom Blackwell

JILA physicists from the National Institute of Standards and Technology (NIST) and University of Colorado Boulder have discovered a new semiconductor quasiparticle called a “quantum droplet” or “dropleton”.

Quasiparticles are groups of smaller particles that act together in a predictable way, and in the dropleton the particles briefly condense into a liquid-like…

New 'leviton' quasiparticle spotted by physicists

A new type of quasiparticle – dubbed the "leviton" – has been seen by physicists in France and Switzerland. First predicted in 1996 by a team led by Leonid Levitov, the phenomenon involves the excitation of as few as one electron to create a wave that propagates coherently through a metal. The ability to make levitons on demand could lead to the creation of quantum-electronics circuits that involve sending single electrons through tiny circuits.

What are Quasi Particles?

The term Quasi particles describes a physical concept, which treats elementary excitations in solids, like spin waves, as particles. As the particles do not consist of matter, they are called quasi particles.

At first it must sound curious to treat excitations as particles. But let us think about what matter is. From Einstein’s relativistic theory we know that matter and energy are essentially the same. Matter can be converted into energy, like in fission and fusion reactors. On the other hand energy can be converted into matter. It happens naturally; when high energy particles or radiation hit the earth’s atmosphere, a whole cascade of secondary particles is created. This phenomenon is called “air shower”. Partially the created particles originate from kinetic energy of incoming high energy particles or they are entirely produced through the energy of a high energy photon. In large particle accelerators, new particles are produced from the impact energy that occurs when two particles with nearly the speed of light collide with each other.

So it seems that what we call matter also consist of elementary excitations of a medium called “space”. Some of these excitations have a very short lifetime like muons or pions for example. Others seem to have infinite lifetimes like protons and electrons. Although it might come out that their lifetime is just incredibly long, so that no decay could be observed till the up come of modern science.

From this point of view it seems not to be weird when we treat elementary excitations in solids as particles. These particles have in most cases finite lifetimes, like the magnon or exciton. But there are also some quasi-particles with infinite lifetime like the cooper-pair in superconductors. We see that there is a striking similarity between matter-particles and quasi-particles and to some extent they can be treated in the same way.

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 Spectroscopic mapping of quasiparticle interference

Quasiparticle interference of heavy superconducting electrons

Quasi-particle interference mapping of topological insulators